1. Field of the Invention
This invention relates to temperature control systems which maintain the temperature of an electronic device near a given set point temperature(s) while the device is being operated or tested. Two specific examples of electronic devices which need to be operated or tested at a constant temperature are packaged integrated chips and unpackaged bare chips.
2. Description of the Related Art
Maintaining the chip temperature near a given set point is not difficult if the power dissipation of the chip is constant or varies in a small range while operating or testing. In such cases, it is only necessary to couple the chip through a fixed thermal resistance to a thermal mass which is at a fixed temperature. But if the instantaneous power dissipation of the chip varies up and down in a wide range while operating or testing, then maintaining the chip temperature near a constant set point is very difficult. When chips are being debugged or tested, it is advantageous to evaluate their performance at a variety of temperatures, ranging from cold to hot. Combining the ability to force temperature across a wide temperature range, while accommodating the temperature changes associated with varying instantaneous power dissipation, is very challenging.
Typical approaches to solve this problem involve forced air convection systems that extend well beyond the desired forcing temperature range at both the hot and cold ends. In this way, an attempt can be made to accelerate the chip""s temperature conditioning by overcooling or overheating. As the nominal power density of the chips continue to increase, the ability of forced air convection systems to overcool reaches practical limits, causing increases in the temperature error between the desired and actual temperatures relative to set point. Another problem is that chips fabricated in the latest processes have an increased sensitivity to high temperatures. The potential for chip damage due to overheating adds risk to the use of the overheating approach. Increased time to set point is the result, with lost utilization of expensive test equipment and engineering personnel as an expense.
Another approach is the use of dual liquid conduction systems, with one hot and one cold liquid. The proportion of the liquids are mechanically metered to affect the desired forcing temperature. To achieve fast response times, this approach requires that the metering occur very close to the chip. This imposes mechanical packaging constraints which limit the flexibility to bring the surface of the temperature forcing system control surface into contact with the chip or chip package. Even so, the mechanical metering of the dual liquids is much slower to affect a change in the forcing temperature when compared to the temperature changes induced by the chip""s instantaneous power dissipation. This also causes increased error between the desired and actual temperatures.
The present invention is directed to overcoming or at least reducing the effects of one or more of the problems set out above.
This invention combines the optimal liquid and liquid temperature control system with a heat exchanger. A single liquid is used to cover as much of the temperature range as possible. Modes of the control of the heating element are then used to extend the set point temperature range which the temperature forcing system contact surface can apply. In one embodiment of the invention, the flow rate of the liquid through the heat exchanger is metered, to optimize the power dissipation of the heat exchanger, versus the desired thermal control performance at the chip.
The present invention provides a liquid based, wide range, fast response chip temperature control system. The wide temperature range is achieved by extending the effective temperature range of a liquid based coolant loop with resistive heating in the control surface. In this way, the desired temperature range for testing chips can be achieved, while supplying the features of: (i) fast set point temperature change, (ii) response to instantaneous power dissipation changes, and (iii) small form factor and flexibility in chip situations.
This system may include: (i) the liquid cooling and recirculation system, (ii) the thermal control circuit which controls the heater temperature, (iii) the algorithms contained in the thermal control circuit which perform the translation from a desired device temperature to a heater control, and (iv) the heat exchanger consisting of a liquid cooled heat sink and a resistive heater bonded to it, which contacts the chip.
Briefly, there is provided according to one embodiment of the present invention an apparatus for controlling a temperature of a device. The apparatus includes a heater, a heat sink, and a temperature control system. The temperature control system is adapted to move the temperature of the point on the heater from approximately a first set point temperature to approximately a second set point temperature.
Briefly, there is provided according to another embodiment of the present invention an apparatus for controlling a temperature of a device. The apparatus includes a heater, a heat sink, and a temperature control system. The temperature control system is adapted to move the temperature of the point on the device from approximately a first set point temperature to approximately a second set point temperature.
Briefly, there is provided according to another embodiment of the present invention an apparatus for controlling a temperature of a device. The apparatus includes a heater, a heat transfer unit, and a temperature control system. The temperature control system is adapted to move the temperature of the point on the device by at least 50 degrees C. by controlling power sent to the heater and by controlling a temperature of a surface of the heat transfer unit.
Briefly, there is provided according to another embodiment of the present invention an apparatus for controlling a temperature of a device. The apparatus includes a heater, a heat sink, and a temperature control system. The temperature control system is coupled to both the heater and the heat sink and is adapted to maintain a temperature of a point on the device at or near a set point temperature despite the existence of self-heating of the device.
Briefly, there is provided according to another embodiment of the present invention an apparatus for controlling a temperature of a semiconductor device during testing. The apparatus includes a heat exchanger and a temperature control system. The heat exchanger is adapted to be thermally coupled to the semiconductor device during testing. The temperature control system is coupled to the heat exchanger and is for controlling the heat exchanger. The temperature control system is adapted to maintain the temperature of the semiconductor device at or near a set point temperature during testing despite self-heating of the semiconductor device. The set point temperature can be set to a first value or to a second value which is at least 25 degrees Celsius lower.
Briefly, there is provided according to another embodiment of the present invention a method of controlling a temperature of a semiconductor device during testing. The method includes moving the temperature of the device to approximately a first set point temperature. The method further includes moving the temperature of the device to approximately a second set point temperature.
Briefly, there is provided according to another embodiment of the present invention an apparatus for controlling a temperature of a semiconductor device. The apparatus includes a heat exchanger, a gas injection fitting, and a temperature control system. The gas injection fitting is for injecting a gas into a contact region between the heat exchanger and the semiconductor device when the semiconductor device is contacting the heat exchanger.